Glucose 6-phosphate stimulation of MgATP-dependent Ca2+ uptake by rat kidney microsomes.
(1) The features of MgATP-dependent Ca2+ accumulation under stimulation with glucose 6-phosphate were studied in rat kidney microsomes. (2) Ca2+ accumulated in the presence of MgATP alone does not exceed approx. 2 nmol/mg protein. (3) Glucose 6-phosphate markedly stimulates Ca2+ accumulation, up to steady-state levels approx. 15-fold higher than in its absence. (4) The hydrolysis of glucose 6-phosphate by glucose-6-phosphatase is essential for the stimulation, as shown by inhibiting the glucose 6-phosphate hydrolysis with adequate concentrations of vanadate. Inorganic phosphate is accumulated in microsomal vesicles during glucose 6-phosphate-stimulated Ca2+ uptake in equimolar amounts with respects to Ca2+. (5) Increasing concentrations of glucose 6-phosphate result in increasing stimulations of Ca2+ uptake, until a maximal Ca2(+)-loading capacity of approx. 27 nmol/mg microsomal protein is reached. It is suggested that the enlargement of the kidney microsomal Ca2+ pool induced by glucose 6-phosphate (an important metabolite in kidney) might play a role in the regulation of Ca2+ homeostasis in kidney tubular cells.
Fulceri
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Istituto di Patologia Generale dell'Università di Siena, Italy.
Romani
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Pompella
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Benedetti
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D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D005958:Glucosephosphates / Q000494:pharmacology*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D005958:Glucosephosphates; D000255:Adenosine Triphosphate